This is really cool, and doesn't require car headlights shining on your bike like reflectors do.

When driving in my car at night, I would occasionally notice some bicycles with reflective strip around the tires. Car headlights just light them up, making it very easy to see a bike from the side. I finally found that many Schwalbe tires have this reflective strip (e.g. http://www.peterwhitecycles.com/schwalbe.asp third paragraph).

I saw a bike the other night with a half-dozen or more of those in-spoke reflectors. Very visible in headlights.